Family #22 in the 1767 Grimm census.
Family #106 in the 1775 Grimm census.
Samuel Rusch was born about 1689 in the Pommern area of what is now Germany. I have not yet identified documents that confirm his birth date, place, and parents.
Samuel married Anna Margaretha, last name unknown for now, and the couple had four children born before 1766. That year, Samuel and his family immigrated from Germany to Russia. They are in the Kulberg Lists, identified as arriving in Russia on 30 September 1766, the last group of German immigrants brought to Russia who were relocated to the Volga region of that country.
Kulberg Lists 
1767 Grimm Census 
In this record, a son Friedrich, age 18, is named. He would have been 17 in 1766 and should have appeared in the Kulberg Lists, but is missing. Daughter Helena is missing and probably was married and living in another household. Catharina is missing, unless her full name was Catharina Maria Dorothea.
The ages of the children are off, but the family probably only gave approximate ages to those collecting personal data.
Note that there was a gap of about 10 years between son Friedrich and the next oldest child, Johann Georg. There were most likely other children born during that time but are not listed here for one reason or another. But a daughter named Anna Dorothea could very well have been born in 1746 or 1747, the woman who married Johann Peter Heide and is listed in his family in the 1767 census. The Heide family lived next door to Samuel Rusch at the time of the 1767 census.
1775 Grimm Census 
Note that daughter Katarina Maria did not appear in the 1767 census, where she should have been identified at age 8. However, daughter Dorothea does appear in the 1767 census at age 10, but not in the 1775 census. Could these be the same person, either misidentified or with three names instead of two, as in Katharina Maria Dorothea?
Samuel Rusch does not appear in the 1798 Grimm census, and he had probably passed away. Had he survived, he would have been 109, which was not likely. He probably passed away closer to 1775, when he was 86, than to 1798.
Have you taken a DNA test? If so, login to add it. If not, see our friends at Ancestry DNA.